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PHEVs emit almost five times greater planet-heating pollution than official data show, according to a new analysis.

Widening Discrepancy In Lab and Actual CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, according to research carried out by a advocacy group. That contrasts significantly with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” stated a lead researcher involved in the report. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs emit almost as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode compared to total distance. The team determined that just 27% of travel was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than official projections. This occurred because electric motors were insufficiently powerful enough to operate alone, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions allowed several major carmaker groups to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 extra annually in running expenses than would be assumed under laboratory tests.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Political Debate and Industry Lobbying

Hybrid cars have recently been brought again into policy debates as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car sector and opposition from EU countries with significant automotive industries.

Several high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One external energy policy expert, who was not involved with the study, called the report a “very useful contribution” after years in which segments of the car sector argued there was too little information to accurately evaluate real-world emissions.

“These findings show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” they said. “All policy changes regarding PHEVs should be implemented with extreme caution and considering that evidence.”